During the first phase of the project, we propose to examine the effects of i.v. and orally administered diazepam and pentobarbital on psychomotor skills related to driving in normal, anxious, sedative-tolerant, and aged populations. There are differences (at least when using a sedative threshold test) between anxious, aged, tolerant, and normal populations in their sensitivity to sedative drugs. Our studies will test for differences between these subject groups in the degree of psychomotor impairment produced by diazepam and pentobarbital. In each subject population the blood concentrations of diazepam and pentobarbital and their metabolites will be correlated with the degree of psychomotor impairment. In addition, we will attempt to develop a more sensitive and accurate test for sedative tolerance in patients who require sedative medication for the treatment of alcohol, barbiturate, and other sedative-hypnotic withdrawal syndromes. Such information will provide the clinician with a more accurate means of assessing the sedative requirements for determining the appropriate daily dose needed to withdraw addicted patients. During the latter phase, we propose to examine the effects of marihuana and/or amphetamine on psychomotor skills related to driving. In the amphetamine studies we will be testing subjects both with and without sleep deprivation.